“It was just epic,” Alan exclaims. “When Kurt screamed out the lyrics to his songs, I’ve never heard anyone with a scream like that. He could’ve stripped paint off the walls.”

After the show, Kurt and Dave, to Alan’s utter delight, hung around for a while to stand and chat to punters. “I got talking to them for a little while,” Alan says, after happily snapping away while his heroes performed mere feet in front of him.

“They could’ve went ‘see you later, bye, bye’ and not given me the time of day. They were just super-cool.”

In between chin-wagging with the two superstars, Alan took yet more photos, incurring the wrath of one doorman.

“One of the bouncers was getting angry because I was taking pictures,” Alan recalls.

“Dave Grohl saw what was going on, walked over, kissed the bouncer and gave him a big hug. The irony is I didn’t get the camera confiscated because of Dave Grohl.”

To put it another way, Alan’s photos survived because the future Foo Fighters man intervened. One of the photos shows the two together, Alan giving the thumbs up, and Dave a simple wave.

In another image, a doe-eyed Kurt is captured staring directly at the camera in a small sea of people. It is, without question, the most evocative of the set.

“I was looking at Kurt Cobain and he was looking at me,” Alan says, passionately. “It was like the whole f****** world had stopped.”

He adds: “That picture captures everything about him. His intensity, his soft side, his good energy, his talent. There’s an incredible power in that picture.”

When Nirvana eventually departed, they left behind a couple of dozen Edinburgh souls for whom open mic nights would never be quite the same again.